1. Field of the Invention
This invention relates to a waste screen for a roof drainage outlet, which is located substantially in the roof plane and consists of an outlet opening in the roof and a plate covering said opening, which plate has such a circumference and vertical distance above the roof plane, that at least at the design flow rate air is prevented from being sucked in beneath the plate edge, and the gap between the plate and roof plane, thus, constitutes the outlet port.
2. Description of the Prior Art
Waste screens for roof drainage outlets are known in various different designs. The simplest type consists of a perforated plate laid above the outflow opening. One requirement, however, is that there must be an outlet through the opening even when the screen is clogged, and that such outlet must comprise a so-called overflow outlet. Screens for roof discharge pipes, therefore, often are designed as cylinders with perforated casing surfaces, and the upper edge of the casing constitutes the overflow edge. This implies that in the a clogged casing surface the water rises and flows over the upper edge of the casing and through the interior of the casing without being screened.